1. Field of the Invention
The present invention relates to a digital video cassette recorder (DVCR) and more particularly, to a method of writing and searching index data for a DVCR.
2. Discussion of the Related Art
For an index search, a video cassette recorder (VCR) displays various programs written on a tape to permit a user to select a desired program and reproduce the program selected by moving the tape to the selected program.
VCR generally modulates a pulse width of a control signal in response to an index signal which is indicative of a start position each of program written on a magnetic tape, and searches for the programs using the modulated control signal and the index signal.
To display a program selected by the user, the index search is performed and a reproducing mode is then performed.
Generally, a video index search system (VISS) and a video address search system (VASS) are used for index search. The VISS performs the index search using only an index signal. The VASS performs the index search using an address signal which is indicative of an absolute address of a tape in addition to the index signal.
An apparatus for writing and searching index data for a DVCR according to the background art will be described with reference to the accompanying drawings.
FIG. 1 is a schematic block diagram illustrating an apparatus for writing and searching index data for a DVCR according to a background art.
Index data is not stored in a certain position of a tape but stored in a cassette memory to which a nonvolatile memory is attached.
In other words, the apparatus for writing and searching index data for a DVCR according to the background art includes a cassette memory (nonvolatile memory) 109 mounted in a certain position of a cassette 101, for writing index data, rotation speed detectors 106 and 107 respectively mounted in a supply reel 104 and a winding reel 105 of the cassette 101, for detecting a rotation speed, a control signal writing/reproducing portion 112 for reproducing and writing a control signal of a cassette tape 102 through a control head 108, an SRAM 115 for temporarily storing the index data in a program writing mode to forward the index data to the cassette memory 109 when ejecting a tape, and a microprocessor 111 for controlling writing/reproduction of the index data in response to an external key signal.
Reference numerals 113 and 114 represent a tape driving portion and a key input portion, respectively. Reference numerals 119, 118 and 117 represent a system controller, a monitor, and a video signal processor, respectively. Reference numeral 116 represents an on screen display (OSD) portion. Also reference numeral 103 represents a rotation drum.
The operation of the apparatus for writing and searching index data for a DVCR according to the background art will be described below.
The microprocessor 111 writes the index data in the SRAM 115 and forwards the same to the cassette memory 109 when ejecting the cassette.
To reproduce the index data in the cassette memory 109, the microprocessor 111 reads the index data stored in the cassette memory 109 and stores the same in the SRAM 15. At the same time, the microprocessor 111 displays the index data in a screen to be recognized by the user. Then, if the user selects a desired program, the microprocessor 111 searches the position of the program selected by the user by checking the remaining amount of the tape in response to a signal input through the rotation speed detectors 106 and 107.
FIG. 2 shows a method of writing and searching index data for a DVCR according to the background art. An additional data region 304 is formed on a tape to write index data. For writing the index data, data in a data signal region 303 is maintained as is, while the index data is written in the additional data region 304.
Reference numerals 301, 302, 305 and 306 represent a magnetic tape, a track, a header region, and a positioning signal, respectively.
The method of writing and searching index data for a DVCR according to the background art has several problems.
The index data is stored in the memory attached to the cassette and read in a reproducing mode. The cassette memory is used for index search. Therefore, it is not economical and some error may occur when checking the remaining amount of the tape and performing the index search. In addition, if the index data is not exactly written in the additional data region on the tape, there is a problem that the index data may be overwritten on video data.